Cartridge with a heater assembly for an aerosol-generating system

ABSTRACT

An aerosol-generating system including a cartridge is provided, the cartridge including a liquid storage portion including a housing configured to hold a liquid aerosol-forming substrate, the housing having an opening; and a heater assembly including at least one heater element fixed to the housing and extending across an opening of the housing, wherein a width of the at least one heater element of the heater assembly is smaller than a width of the opening of the housing. The heater element may be spaced from a periphery of the opening, leading to more efficient heating and aerosol production.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims benefit under 35 U.S.C.§ 120 to U.S. application Ser. No. 17/669,162, filed Feb. 10, 2022,which is a continuation of and claims benefit under 35 U.S.C. § 120 toU.S. application Ser. No. 16/877,412, filed May 18, 2020 (now U.S. Pat.No. 11,272,581), which is a continuation of and claims benefit under 35U.S.C. § 120 to U.S. application Ser. No. 15/117,620, filed Aug. 9, 2016(now U.S. Pat. No. 10,687,552), which is a U.S.

National Stage of PCT/EP2014/077840, filed on Dec. 15, 2014, which isbased upon and claims benefit of priority under 35 U.S.C. § 119 fromEuropean Patent Application No. 14154552.5, filed Feb. 10, 2014,European Patent Application No. 14154553.3, filed Feb. 10, 2014, andEuropean Patent Application No. 14154554.1, filed Feb. 10, 2014, theentire contents of each of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to aerosol-generating systems and to acartridge for aerosol-generating systems that comprises a heaterassembly that is suitable for vaporising a liquid. In particular, theinvention relates to handheld aerosol-generating systems, such aselectrically operated smoking systems. Aspects of the invention relateto a heater element for an aerosol-generating system.

DESCRIPTION OF THE RELATED ART

One type of aerosol-generating system is an electrically operatedsmoking system. Handheld electrically operated smoking systemsconsisting of a device portion comprising a battery and controlelectronics, and a cartridge portion comprising a supply ofaerosol-forming substrate, and an electrically operated vapouriser, areknown. A cartridge comprising both a supply of aerosol-forming substrateand a vapouriser is sometimes referred to as a “cartomiser”. Thevapouriser typically comprises a coil of heater wire wound around anelongate wick soaked in liquid aerosol-forming substrate. The cartridgeportion typically comprises not only the supply of aerosol-formingsubstrate and an electrically operated vapouriser, but also amouthpiece, which the user sucks on in use to draw aerosol into theirmouth.

Thus, electrically operated smoking systems that vaporize a liquid byheating to form an aerosol typically comprise a coil of wire that iswrapped around a capillary material that holds the liquid. Electriccurrent passing through the wire causes resistive heating of the wirewhich vaporises the liquid in the capillary material. The capillarymaterial is typically held within an airflow path so that air is drawnpast the wick and entrains the vapour. The vapour subsequently cools toform an aerosol.

This type of system can be effective at producing aerosol but it canalso be challenging to manufacture in a low cost and repeatable way.Furthermore, the wick and coil assembly, together with associatedelectrical connections, can be fragile and difficult to handle.

Alternatively, systems such as those proposed in US 204/020454, userectangular cartridges having sheet-like composites that include anintegrally formed wick and heating element have been proposed. Suchsystems require filing of the cartridge through a hole. Integrallyforming the wick and heating element introduces additional complexityinto the manufacturing process. Moreover, it is desirable to overcomethe need to fill a rectangular shaped cartridge through a hole as thisintroduces additional complexity to the manufacturing of the completedcartridge.

SUMMARY

It would be desirable to provide a heater assembly suitable for anaerosol-generating system, such as a handheld electrically operatedsmoking system, that is more inexpensive to produce and is robust. Itwould be further desirable to provide a heater assembly that is asefficient or more efficient than prior heater assemblies inaerosol-generating systems.

In one aspect there is provided a cartridge for use in an electricallyoperated aerosol-generating system, comprising: a liquid storage portioncomprising a housing for holding a liquid aerosol-forming substrate, thehousing having an opening; and a heater assembly comprising at least oneheater element fixed to the housing and extending across the opening ofthe housing, wherein the at least one heater element of the heaterassembly has a width that is smaller than a width of the opening of thehousing.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying drawings, in which:

FIGS. 1A to 1D are schematic illustrations of a system, incorporating acartridge, in accordance with an embodiment of the invention;

FIGS. 2A and 2B are exploded views of an example cartridge of a systemshown in FIGS. 1A to 1D;

FIG. 3 shows a heater assembly with three heater elements;

FIG. 4 shows a heater assembly with four heater elements; and

FIG. 5 is a diagram showing the TPM yield of different heatergeometries.

DETAILED DESCRIPTION

The opening of the cartridge has a width and a length dimension. The atleast one heater element extends across the full length dimension of theopening of the housing. The width dimension is the dimensionperpendicular to the length dimension in the plane of the opening.Preferably the at least one heater element of the heater assembly has awidth that is smaller than the width of the opening of the housing.

Preferably a part of the heater element is spaced apart from theperimeter of the opening. Where the heater element comprises a stripattached to the housing at each end, preferably the sides of the stripdo not contact the housing. Preferably there is a space between thesides of the strip and the perimeter of the opening.

The width of the heater element may be less than the width of theopening in at least a region of the opening. The width of the heaterelement may be less than the width of the opening in all of the opening.

The width of the at least one heater element of the heater assembly maybe less than 90%, for example less than 50%, for example less than 30%,for example less than 25% of the width of the opening of the housing.

The area of the heater element may be less than 90%, for example lessthan 50%, for example less than 30%, for example less than 25% of thearea of the opening of the housing. The area of the heater elements ofthe heater assembly may be for example between 10% and 50% of the areaof the opening, preferably between 15 and 25% of the area of theopening.

The heater element preferably is supported on an electrically insulatingsubstrate. The insulating substrate preferably has an aperture definingthe opening of the housing. The opening may be of any appropriate shape.For example the opening may have a circular, square or rectangularshape. The area of the opening may be small, preferably less than orequal to about 25 mm².

The at least one heater element is preferably arranged in such a waythat the physical contact area with the substrate is reduced comparedwith a case in which the heater elements of the heater assembly is incontact around the whole of the periphery of the opening. The at leastone heater element preferably does not directly contact the perimeterwindow side walls of the opening. In this way thermal contact to thesubstrate is reduced and heat losses to the substrate and furtheradjacent elements of the aerosol-generating system are reduced.

Without wishing to be bound by any particular theory, it is believedthat by spacing the heater element away from the housing opening, lessheat is transferred to the housing, thus increasing efficiency ofheating and therefore aerosol generation. It is also thought that wherethe heating element is close to or in contact with the periphery of theopening, there is heating of liquid which is located away from theopening. This heating is thought to lead to inefficiency because suchheated liquid away from the opening is not able to be utilised in theformation of the aerosol. By spacing the heating element away from theperiphery of the opening in the housing, more efficient heating of theliquid, or production of the aerosol may be obtainable.

The spacing between the heater element and the opening periphery ispreferably dimensioned such that the thermal contact is significantlyreduced. The spacing between the heater element and the openingperiphery may be between 25 and 40 microns.

The aerosol generating system may be an electrically operated smokingsystem.

The substrate preferably comprises at least first and secondelectrically conductive contact portions for contacting the at least oneheater element, the first and second electrically conductive contactportions positioned on opposing sides of the opening to one another,wherein the first and second electrically conductive contact portionsare configured to allow contact with an external power supply.

The heater assembly may comprise a plurality of heater elementselectrically connected in series. The first and second electricallyconductive contact portions may be arranged such that the first contactportion contacts the first heater element and the second contact portioncontacts the last heater element of the serially connected heaterelements. Additional contact portions are provided at the heaterassembly to allow for serial connection of all heater elements.Preferably these additional contact portions are provided at each sideof the opening of the substrate.

Preferably, where the heater assembly includes a plurality of heaterelements, the heater elements are spatially arranged substantially inparallel to each other. Preferably the heater elements are spaced apartfrom each other. Without wishing to be bound by any particular theory,it is thought that spacing the heater elements apart from each other maygive more efficient heating. By appropriate spacing of the heaterelements for example, a more even heating across the area of the openingmay be obtained compared with for example where a single heating elementhaving the same area is used.

In a particular preferred embodiment, the heater assembly comprises anodd number of heater elements, preferably three or five heater elements,and the first and second contact portions are located on opposite sidesof the aperture of the substrate. This arrangement has the advantagethat the first and second contact portions are arranged on oppositesides of the aperture.

The heater assembly may alternatively comprise an even number of heaterelements, preferably two or four heater elements. In this embodiment thecontact portions are preferably located on the same side of thecartridge. With this arrangement a rather compact design of the electricconnection of the heater assembly to the power source may be achieved.

The at least one heater element may each be formed from a plurality ofelectrically conductive filaments, which may form a mesh or array offilaments or may comprise a woven or non-woven fabric. The heaterelement may be fluid permeable.

In some examples, the at least one heater element has a first face thatis fixed to the electrically insulating substrate and the first andsecond electrically conductive contact portions are configured to allowcontact with an external power supply on a second face of the heaterelement opposite to the first face.

The system may further comprise a liquid storage portion comprising ahousing containing a liquid aerosol-forming substrate, wherein theheater assembly is fixed to the housing of the liquid storage portion.The housing may be a rigid housing and impermeable to fluid. As usedherein “rigid housing” means a housing that is self-supporting. Therigid housing of the liquid storage portion preferably providesmechanical support to the heater assembly.

The liquid storage portion may comprise a capillary material configuredto convey liquid aerosol-forming substrate to the heater assembly.

The provision of a heater assembly of this type in an aerosol-generatingsystem has several advantages over a conventional wick and coilarrangement. A heater element comprising a mesh or array of filamentsallows for a greater area of the heater to be in contact with a liquidbeing vaporized. The heater assembly can be inexpensively produced,using readily available materials and using mass production techniques.The heater assembly is robust allowing it to be handled and fixed toother parts of the aerosol-generating system during manufacture, and inparticular to form part of a removable cartridge. The provision ofelectrically conductive contact portions forming part of the heaterelement allows for reliable and simple connection of the heater assemblyto a power supply.

The electrically conductive filaments may be substantially flat. As usedherein, “substantially flat” preferably means formed in a single planeand for example not wrapped around or other conformed to fit a curved orother non-planar shape. A flat heater assembly can be easily handledduring manufacture and provides for a robust construction.

The heater element or heater assembly may be substantially flat.

The at least one heater element may comprise a mesh having intersticesbetween the electrically conductive filaments.

In such an arrangement, preferably at least a portion of the heaterelement is spaced apart from the periphery of the opening by a distancewhich is greater than a dimension of the interstices of that portion ofthe heater element.

The electrically conductive filaments may define interstices between thefilaments and the interstices may have a width of between 10 μm and 100μm. Preferably the filaments give rise to capillary action in theinterstices, so that in use, liquid to be vaporized is drawn into theinterstices, increasing the contact area between the heater assembly andthe liquid.

The electrically conductive filaments may form a mesh of size between160 and 600 Mesh US (+/−10%) (i.e. between 160 and 600 filaments perinch (+/−10%)). The width of the interstices is preferably between 75 μmand 25 μm. The percentage of open area of the mesh, which is the rationof the area of the interstices to the total area of the mesh ispreferably between 25 and 56%. The mesh may be formed using differenttypes of weave or lattice structures. Alternatively, the electricallyconductive filaments consist of an array of filaments arranged parallelto one another.

The mesh, array or fabric of electrically conductive filaments may alsobe characterised by its ability to retain liquid, as is well understoodin the art.

The electrically conductive filaments may have a diameter of between8μμm and 100 μm, preferably between 8 μm and 50 μm, and more preferablybetween 8 μm and 39 μm. The filaments may have a round cross section ormay have for example a flattened cross section.

The area of the mesh, array or fabric of electrically conductivefilaments of a single heater element may be small, preferably less thanor equal to 25 mm², allowing it to be incorporated in to a handheldsystem. The heater element may, for example, be rectangular and have alength of about 5 mm and a width of about 2 mm. In some examples, thewidth is below 2 mm, for example the width is about 1 mm. The smallerthe width of the heater elements, the more heater elements may beconnected in series in the heater assembly of the present invention. Anadvantage of using smaller width heater elements that are connected inseries is that the electric resistance of the combination of heaterelements is increased.

The heater element may cover an area of between 10% and 50% of the areaof the heater assembly. The mesh or array of electrically conductivefilaments covers an area of between 15 and 25% of the area of the heaterassembly.

The electrically conductive filaments may comprise any suitableelectrically conductive material. Suitable materials include but are notlimited to: semiconductors such as doped ceramics, electrically“conductive” ceramics (such as, for example, molybdenum disilicide),carbon, graphite, metals, metal alloys and composite materials made of aceramic material and a metallic material. Such composite materials maycomprise doped or undoped ceramics. Examples of suitable doped ceramicsinclude doped silicon carbides. Examples of suitable metals includetitanium, zirconium, tantalum and metals from the platinum group.Examples of suitable metal alloys include stainless steel, constantan,nickel-, cobalt-, chromium-, aluminium- titanium- zirconium-, hafnium-,niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-, manganese-and iron-containing alloys, and super-alloys based on nickel, iron,cobalt, stainless steel, Timetal®, iron-aluminium based alloys andiron-manganese-aluminium based alloys. Timetal® is a registered trademark of Titanium Metals Corporation. The filaments may be coated withone or more insulators. Preferred materials for the electricallyconductive filaments are 304, 316, 304L, and 316L stainless steel, andgraphite.

The electrical resistance of the mesh, array or fabric of electricallyconductive filaments of the heater element is preferably between 0.3 and4 Ohms. More preferably, the electrical resistance of the mesh, array orfabric of electrically conductive filaments is between 0.5 and 3 Ohms,and more preferably about 1 Ohm. The electrical resistance of the mesh,array or fabric of electrically conductive filaments is preferably atleast an order of magnitude, and more preferably at least two orders ofmagnitude, greater than the electrical resistance of the contactportions. This ensures that the heat generated by passing currentthrough the heater element is localised to the mesh or array ofelectrically conductive filaments. It is generally advantageous to havea low overall resistance for the heater element if the system is poweredby a battery. Minimizing parasitic losses between the electricalcontacts and the mesh or the filaments is also desirable to minimizeparasitic power losses. A low resistance, high current system allows forthe delivery of high power to the heater element. This allows the heaterelement to heat the electrically conductive filaments to a desiredtemperature quickly.

The electrically conductive contact portions may be fixed directly tothe electrically conductive filaments. The contact portions may bepositioned between the electrically conductive filaments and theelectrically insulating substrate. For example, the contact portions maybe formed from a copper foil that is plated onto the insulatingsubstrate. The contact portions may also bond more readily with thefilaments than the insulating substrate would.

Alternatively, the electrically conductive contact portions may beintegral with the electrically conductive filaments of the heaterelements. For example, the heater element may be formed by etching aconductive sheet to provide a plurality of filaments between two contactportions.

At least one heater element of the heater assembly may comprise at leastone filament made from a first material and at least one filament madefrom a second material different from the first material. This may bebeneficial for electrical or mechanical reasons. For example, one ormore of the filaments may be formed from a material having a resistancethat varies significantly with temperature, such as an iron aluminiumalloy. This allows a measure of resistance of the filaments to be usedto determine temperature or changes in temperature. This can be used ina puff detection system and for controlling heater temperature to keepit within a desired temperature range.

The electrically insulating substrate may comprise any suitablematerial, and is preferably a material that is able to tolerate hightemperatures (in excess of 300 degree Celsius) and rapid temperaturechanges. An example of a suitable material is a polyimide film, such asKapton®.

The aerosol-forming substrate is a substrate capable of releasingvolatile compounds that can form an aerosol. The volatile compounds maybe released by heating the aerosol-forming substrate.

The aerosol-forming substrate may comprise plant-based material. Theaerosol-forming substrate may comprise tobacco. The aerosol-formingsubstrate may comprise a tobacco-containing material containing volatiletobacco flavour compounds, which are released from the aerosol-formingsubstrate upon heating. The aerosol-forming substrate may alternativelycomprise a non-tobacco-containing material. The aerosol-formingsubstrate may comprise homogenised plant-based material. Theaerosol-forming substrate may comprise homogenised tobacco material. Theaerosol-forming substrate may comprise at least one aerosol-former. Anaerosol-former is any suitable known compound or mixture of compoundsthat, in use, facilitates formation of a dense and stable aerosol andthat is substantially resistant to thermal degradation at the operatingtemperature of operation of the system. Suitable aerosol-formers arewell known in the art and include, but are not limited to: polyhydricalcohols, such as triethylene glycol, 1,3-butanediol and glycerine;esters of polyhydric alcohols, such as glycerol mono-, di- ortriacetate; and aliphatic esters of mono-, di- or polycarboxylic acids,such as dimethyl dodecanedioate and dimethyl tetradecanedioate.Preferred aerosol formers are polyhydric alcohols or mixtures thereof,such as triethylene glycol, 1,3-butanediol and, most preferred,glycerine. The aerosol-forming substrate may comprise other additivesand ingredients, such as flavourants.

The housing of the liquid storage portion may contain a capillarymaterial and the capillary material may extend into the intersticesbetween the filaments.

The capillary material may have a fibrous or spongy structure. Thecapillary material preferably comprises a bundle of capillaries. Forexample, the capillary material may comprise a plurality of fibres orthreads or other fine bore tubes. The fibres or threads may be generallyaligned to convey liquid to the heater. Alternatively, the capillarymaterial may comprise sponge-like or foam-like material. The structureof the capillary material forms a plurality of small bores or tubes,through which the liquid can be transported by capillary action. Thecapillary material may comprise any suitable material or combination ofmaterials. Examples of suitable materials are a sponge or foam material,ceramic- or graphite-based materials in the form of fibres or sinteredpowders, foamed metal or plastics material, a fibrous material, forexample made of spun or extruded fibres, such as cellulose acetate,polyester, or bonded polyolefin, polyethylene, terylene or polypropylenefibres, nylon fibres or ceramic. The capillary material may have anysuitable capillarity and porosity so as to be used with different liquidphysical properties. The liquid has physical properties, including butnot limited to viscosity, surface tension, density, thermalconductivity, boiling point and vapour pressure, which allow the liquidto be transported through the capillary device by capillary action.

The capillary material may be in contact with the electricallyconductive filaments. The capillary material may extend into intersticesbetween the filaments. The heater assembly may draw liquidaerosol-forming substrate into the interstices by capillary action. Thecapillary material may be in contact with the electrically conductivefilaments over substantially the entire extent of the aperture.

The housing may contain two or more different capillary materials,wherein a first capillary material, in contact with the heater element,has a higher thermal decomposition temperature and a second capillarymaterial, in contact with the first capillary material but not incontact with the heater element has a lower thermal decompositiontemperature. The first capillary material effectively acts as a spacerseparating the heater element from the second capillary material so thatthe second capillary material is not exposed to temperatures above itsthermal decomposition temperature. As used herein, “thermaldecomposition temperature” means the temperature at which a materialbegins to decompose and lose mass by generation of gaseous by products.The second capillary material may advantageously occupy a greater volumethan the first capillary material and may hold more aerosol-formingsubstrate that the first capillary material. The second capillarymaterial may have superior wicking performance to the first capillarymaterial. The second capillary material may be a less expensive or havea higher filling capability than the first capillary material. Thesecond capillary material may be polypropylene.

The first capillary material may separate the heater assembly from thesecond capillary material by a distance of at least 1.5 mm, andpreferably between 1.5 and 2 mm in order to provide a sufficienttemperature drop across the first capillary material.

The liquid storage portion may be positioned on a first side of theelectrically conductive filaments and an airflow channel positioned onan opposite side of the electrically conductive filaments to the liquidstorage portion, such that air flow past the electrically conductivefilaments entrains vapourised liquid aerosol-forming substrate.

The system may further comprise electric circuitry connected to theheater element and to an electrical power source, the electric circuitryconfigured to monitor the electrical resistance of the heater element orof one or more filaments of the heater element, and to control thesupply of power to the heater element from the power source dependent onthe electrical resistance of the heater element or specifically theelectrical resistance of the one or more filaments.

The electric circuitry may comprise a microprocessor, which may be aprogrammable microprocessor, a microcontroller, or an applicationspecific integrated chip (ASIC) or other electronic circuitry capable ofproviding control. The electric circuitry may comprise furtherelectronic components. The electric circuitry may be configured toregulate a supply of power to the heater. Power may be supplied to theheater element continuously following activation of the system or may besupplied intermittently, such as on a puff by puff basis. The power maybe supplied to the heater element in the form of pulses of electricalcurrent.

The system advantageously comprises a power supply, typically a batterysuch as a lithium iron phosphate battery, within the main body of thehousing. As an alternative, the power supply may be another form ofcharge storage device such as a capacitor. The power supply may requirerecharging and may have a capacity that allows for the storage of enoughenergy for one or more smoking experiences. For example, the powersupply may have sufficient capacity to allow for the continuousgeneration of aerosol for a period of around six minutes, correspondingto the typical time taken to smoke a conventional cigarette, or for aperiod that is a multiple of six minutes. In another example, the powersupply may have sufficient capacity to allow for a predetermined numberof puffs or discrete activations of the heater.

The system may comprise a main unit and a cartridge that is removablycoupled to the main unit, wherein the liquid storage portion and heaterassembly are provided in the cartridge and the main unit comprises apower supply. As used herein, the cartridge being “removably coupled” tothe device means that the cartridge and device can be coupled anduncoupled from one another without significantly damaging either thedevice or the cartridge.

The system may be an electrically operated smoking system. The systemmay be a handheld aerosol-generating system. The aerosol-generatingsystem may have a size comparable to a conventional cigar or cigarette.The smoking system may have a total length between approximately 30 mmand approximately 150 mm. The smoking system may have an externaldiameter between approximately 5 mm and approximately 30 mm.

The electrically insulating substrate may be a flexible sheet material.The electrically conductive contact portions and electrically conductivefilaments may be integrally formed with one another.

As used herein, “electrically conductive” means formed from a materialhaving a resistivity of 1×10⁻⁴ Ωm, or less. As used herein,“electrically insulating” means formed from a material having aresistivity of 1×10⁴ Ωm or more.

The present invention is also directed to an aerosol-generating system,preferably an electrically operated smoking system, comprising acartridge according to the present invention.

The aerosol-generating system further comprises a main unit, to whichthe cartridge is removably coupled. The liquid storage portion and theheater assembly are provided in the cartridge and the main unitcomprises a power supply. Different arrangements are possible.

The cartridge can be exchanged after consumption. As the cartridge holdsthe liquid and the heater assembly, the heater assembly is alsoexchanged regularly such that the optimal vaporization conditions aremaintained even after longer use of the main unit.

The aerosol-generating system preferably further comprises electriccircuitry connected to the heater assembly and to an electrical powersource. The electric circuitry is configured to monitor the electricalresistance of the heater assembly or of one or more filaments of aheater element of the heater assembly, and to control a supply of powerfrom the electrical power source to the heater assembly dependent on theelectrical resistance of the heater assembly or the one or morefilaments. By monitoring the temperature of the heater element, thesystem can prevent over-or under-heating of the heater assembly andensure that optimal vaporization conditions are provided.

The present invention is also directed to a method of manufacture of acartridge for use in an aerosol-generating system, for example anelectrically operated aerosol-generating system, comprising the steps ofproviding a liquid storage portion with a housing having an opening,filling the liquid storage portion with liquid aerosol-forming substrateand providing a heater assembly comprising at least one heater elementextending across the opening of the housing wherein the heater elementis smaller than the opening. The width of the at least one heaterelement of the heater assembly may be less than 90%, preferably lessthan 50, further preferably less than 30%, most preferably less than 25%of the width of the opening of the housing.

The heater assembly and the heater element or elements are preferablyfluid permeable. As used herein “fluid permeable” in relation to aheater assembly means that the aerosol-forming substrate, in a gaseousphase and possibly in a liquid phase, can readily pass through theheater assembly or heater element.

The term “substantially flat” filament arrangement is used to refer to afilament arrangement that is preferably in the form of a substantiallytwo dimensional topological manifold. Thus, the substantially flatfilament arrangement extends in two dimensions along a surfacesubstantially more than in a third dimension. In particular, thedimensions of the substantially flat filament arrangement in the twodimensions within the surface are at least 5 times larger than in thethird dimension, normal to the surface. An example of a substantiallyflat filament arrangement is a structure between two substantiallyparallel surfaces, wherein the distance between these two surfaces issubstantially smaller than the extension within the surfaces. In someembodiments, the substantially flat filament arrangement is planar. Inother embodiments, the substantially flat filament arrangement is curvedalong one or more dimensions, for example forming a dome shape or bridgeshape.

The term “filament” is used preferably to refer to an electrical patharranged between two electrical contacts. A filament may arbitrarilybranch off and diverge into several paths or filaments, respectively, ormay converge from several electrical paths into one path. A filament mayhave a round, square, flat or any other form of cross-section. Afilament may be arranged in a straight or curved manner.

The term “filament arrangement” is used preferably to refer to anarrangement of one or preferably a plurality of filaments. The filamentarrangement may be an array of filaments, for example arranged parallelto each other. Preferably, the filaments may form a mesh. The mesh maybe woven or non-woven.

FIGS. 1A to 1D are schematic illustrations of an aerosol-generatingsystem, including a cartridge in accordance with an embodiment of theinvention. FIG. 1A is a schematic view of an aerosol-generating device10 and a separate cartridge 20, which together form theaerosol-generating system. In this example, the aerosol-generatingsystem is an electrically operated smoking system.

The cartridge 20 contains an aerosol-forming substrate and is configuredto be received in a cavity 18 within the device. Cartridge 20 should bereplaceable by a user when the aerosol-forming substrate provided in thecartridge is depleted. FIG. 1A shows the cartridge 20 just prior toinsertion into the device, with the arrow 1 in FIG. 1A indicating thedirection of insertion of the cartridge.

The aerosol-generating device 10 is portable and has a size comparableto a conventional cigar or cigarette. The device 10 comprises a mainbody 11 and a mouthpiece portion 12. The main body 11 contains a battery14, such as a lithium iron phosphate battery, control electronics 16 anda cavity 18. The mouthpiece portion 12 is connected to the main body 11by a hinged connection 21 and can move between an open position as shownin FIG. 1C and a closed position as shown in FIG. 1D. The mouthpieceportion 12 is placed in the open position to allow for insertion andremoval of cartridges 20 and is placed in the closed position when thesystem is to be used to generate aerosol, as will be described. Themouthpiece portion comprises a plurality of air inlets 13 and an outlet15. In use, a user sucks or puffs on the outlet to draw air from the airinlets 13, through the mouthpiece portion to the outlet 15, andthereafter into the mouth or lungs of the user. Internal baffles 17 areprovided to force the air flowing through the mouthpiece portion 12 pastthe cartridge, as will be described.

The cavity 18 has a circular cross-section and is sized to receive ahousing 24 of the cartridge 20. Electrical connectors 19 are provided atthe sides of the cavity 18 to provide an electrical connection betweenthe control electronics 16 and battery 14 and corresponding electricalcontacts on the cartridge 20.

FIG. 1B shows the system of FIG. 1A with the cartridge inserted into thecavity 18, and the cover 26 being removed. In this position, theelectrical connectors rest against the electrical contacts on thecartridge, as will be described.

FIG. 1C shows the system of FIG. 1B with the cover 26 fully removed andthe mouthpiece portion 12 being moved to a closed position.

FIG. 1D shows the system of FIG. 1C with the mouthpiece portion 12 inthe closed position. The mouthpiece portion 12 is retained in the closedposition by a clasp mechanism, as is schematically illustrated in FIG.1D. FIG. 1D illustrates the main body 11 and mouthpiece portion 12connected by hinged connection 21. It will be apparent to a person ofordinary skill in the art that other suitable mechanisms for retainingthe mouthpiece in a closed position may be used, such as a snap fittingor a magnetic closure.

The mouthpiece portion 12 in a closed position retains the cartridge inelectrical contact with the electrical connectors 19 so that a goodelectrical connection is maintained in use, whatever the orientation ofthe system is. The mouthpiece portion 12 may include an annularelastomeric element that engages a surface of the cartridge and iscompressed between a rigid mouthpiece housing element and the cartridgewhen the mouthpiece portion 12 is in the closed position. This ensuresthat a good electrical connection is maintained despite manufacturingtolerances.

Of course other mechanisms for maintaining a good electrical connectionbetween the cartridge and the device may, alternatively or in addition,be employed. For example, the housing 24 of the cartridge 20 may beprovided with a thread or groove (not illustrated) that engages acorresponding groove or thread (not illustrated) formed in the wall ofthe cavity 18. A threaded engagement between the cartridge and devicecan be used to ensure the correct rotational alignment as well asretaining the cartridge in the cavity and ensuring a good electricalconnection. The threaded connection may extend for only half a turn orless of the cartridge, or may extend for several turns. Alternatively,or in addition, the electrical connectors 19 may be biased into contactwith the contacts on the cartridge.

FIGS. 2A and 2B are exploded views of a cartridge 20 suitable for use inan aerosol-generating system, for example an aerosol-generating systemof the type of FIGS. 1A-1D. As shown in FIGS. 2A and 2B, cartridge 20comprises a generally circular cylindrical housing 24 that has a sizeand shape selected to be received into a corresponding cavity of, ormounted in an appropriate way with other elements of theaerosol-generating system, for example cavity 18 of the system of FIGS.1A-1D. The housing 22 contains a capillary material 22 that is soaked ina liquid aerosol-forming substrate. In this example the aerosol-formingsubstrate comprises 39% by weight glycerine, 39% by weight propyleneglycol, 20% by weight water and flavourings, and 2% by weight nicotine.A capillary material is a material that actively conveys liquid from oneend to another, and may be made from any suitable material. In thisexample the capillary material is formed from polyester.

The housing 22 has an open end to which a heater assembly 30 is fixed.The heater assembly 30 comprises a substrate 34 having an aperture 35formed in it, a pair of electrical contacts 32 fixed to the substrateand separated from each other by a gap 33, and a heater element 36formed from a mesh of electrically conductive heater filaments (as shownin FIG. 2A) or an electrical heating element arranged in a curved manner(as shown in FIG. 2B), spanning the aperture 35 and fixed to theelectrical contacts 32 on opposite sides of the aperture 35.

The heater assembly 30 is covered by a removable cover 26. The cover 26comprises a liquid impermeable plastic sheet that is glued to the heaterassembly but which can be easily peeled off. A tab is provided on theside of the cover 26 to allow a user to grasp the cover when peeling itoff. It will now be apparent to one of ordinary skill in the art thatalthough gluing is described as the method to a secure the impermeableplastic sheet to the heater assembly 30, other methods familiar to thosein the art may also be used including heat sealing or ultrasonicwelding, so long as the cover 26 may easily be removed by a consumer.

It will be understood that other cartridge designs are possible. Forexample, the capillary material with the cartridge may comprise two ormore separate capillary materials, or the cartridge may comprise a tankfor holding a reservoir of free liquid.

The heater element 36 (e.g., the mesh of filaments as shown in FIG. 2A,or the electrical heating element arranged in a curved manner as shownin FIG. 2B) are exposed through the aperture in the substrate 34 so thatvapourised aerosol-forming substrate can escape into the airflow pastthe heater assembly.

In use, the cartridge 20 is placed in the aerosol-generating system, andthe heater assembly 30 is contacted to a power source comprised in theaerosol-generating system. An electronic circuitry is provided to powerthe heater element 36 and to volatilize the aerosol-generatingsubstrate.

In FIG. 3 an example of the heater assembly 30 of the present inventionis depicted, in which three substantially parallel heater elements 36 a,36 b, 36 c are electrically connected in series. The heater assembly 30comprises an electrically insulating substrate 34 having a squareaperture 35 formed in it. The size of the aperture is 5 mm×5 mm in thisexample, although it will be appreciated that other shapes and sizes ofaperture could be used as appropriate for the particular application ofthe heater. A first and a second electrical contact 32 a, 32 b areprovided at opposite sides of the aperture 35 and extend substantiallyparallel to the side edges 35 a, 35 b of the aperture Two additionalcontacts 32 c, 32 d are provided adjacent parts of opposing side edges35 c, 35 d of the aperture 35. The first heater element is connectedbetween the first contact portion 32 a and the additional contactportion 32 c. The second heater element 36 b is connected betweenadditional contact portion 32 c and additional contact portion 32 d. Thethird heater element 36 c is connected between additional contactportion 32 c and the second contact portion 32 b. In this embodiment theheater assembly 30 comprises an odd number of heater elements 36, namelythree heater elements and the first and second contact portions 32 a, 32b are located on opposite sides of the aperture 35 of the substrate 34.Heater elements 36 a and 36 c are spaced from the side edges 35 a, ofthe aperture such that there is no direct physical contact between theseheater elements 36 a, 36 c and the insulating substrate 34. Withoutwishing to be bound by any particular theory, it is thought that thisarrangement can reduces heat transfer to the insulating substrate 34 andcan allow for effective volatilization of the liquid aerosol-generatingsubstrate. In FIG. 4 a further example of the heater assembly 30 of thepresent invention is depicted, in which four heater elements 36 a, 36 b,36 c, 36 d are electrically connected in series. The heater assembly 30comprises an electrically insulating substrate 34 having a squareaperture 35 formed in it. The size of the aperture is 5 mm×5 mm. A firstand a second contact portion 32 a, 32 b is provided adjacent an upperand lower portion, respectively, of the same side edge 35 b of theaperture 35. Three additional contact portions 32 c, 32 d, 32 e areprovided, wherein two contact portions are provided adjacent parts ofopposing side edge 35 a, and one contact portion is provided parallel toside edge 35 b between the first and second contact portions 32 a, 32 b.The four heater elements 36 a,36 b, 36 c, 36 d are connected in seriesbetween the these five contact portions 32 a, 32 c, 32 d, 32 e, 32 b asillustrated in FIG. 4 . Again none of the long side edges of the heaterelements is in direct physical contact with any of the side edges of theaperture such that again heat transfer to the insulating substrate isreduced.

In this embodiment the heater assembly 30 comprises an even number ofheater elements 36, namely four heater elements 36 a, 36 b, 36 c, 36 dand the first and second contact portions 32 a, 32 b are located on thesame side of the aperture 35 of the substrate 34.

In arrangements such as that shown in FIGS. 3 and 4 , the arrangement ofthe heater elements may be such that the gap between adjacent heaterelements is substantially the same. For example, the heater elements maybe regularly spaced across the width of the aperture 35. In otherarrangements, different spacings between the heater elements may beused, for example to obtain a desired heating profile. Other shapes ofaperture or of the heater elements may be used.

The heater assembly may comprise a mesh formed from 304L stainlesssteel, with a mesh size of about 400 Mesh US (about 400 filaments perinch). The filaments have a diameter of around 16 μm. The mesh isconnected to electrical contacts 32 that are separated from each otherby a gap and are formed from a copper foil having a thickness of around30 μm. The electrical contacts 32 are provided on a polyimide substrate34 having a thickness of about 120 μm. The filaments forming the meshdefine interstices between the filaments. The interstices in thisexample have a width of around 37 μm, although larger or smallerinterstices may be used. Using a mesh of these approximate dimensionsallows a meniscus of aerosol-forming substrate to be formed in theinterstices, and for the mesh of the heater assembly to drawaerosol-forming substrate by capillary action. The open area of themesh, i.e. the ratio of the area of interstices to the total area of themesh is advantageously between 25 and 56%. The total resistance of theheater assembly is around 1 Ohm. The mesh provides the vast majority ofthis resistance so that the majority of the heat is produced by themesh. In this example the mesh has an electrical resistance more than100 times higher than the electrical contacts 32.

The substrate 34 is electrically insulating and, in this example, isformed from a polyimide sheet having a thickness of about 120 μm. Thesubstrate is circular and has a diameter of 8 mm. The mesh isrectangular and in some examples has side lengths of 5 mm and 2 mm.These dimensions allow for a complete system having a size and shapesimilar to a convention cigarette or cigar to be made. Another exampleof dimensions that have been found to be effective is a circularsubstrate of diameter 5 mm and a rectangular mesh of 1 mm×4 mm.

In an alternative, heater assembly in accordance with the disclosure,the mesh 36 can be replaced by an array of parallel electricallyconductive filaments. The array of filaments is formed from 304Lstainless steel and have a diameter of around 16 μm.

The filaments may be bonded directly to the substrate 34, the contacts32 then being bonded onto the filaments. The contacts 32 are separatedfrom each other by an insulating gap, and are formed from copper foil ofa thickness of around 30 μm. The same arrangement of substrate filamentsand contacts can be used for a mesh type heater. Having the contacts asan outermost layer can be beneficial for providing reliable electricalcontact with a power supply.

The heater assembly may comprise a plurality of heater filaments thatare integrally formed with electrical contacts. Both the filaments andthe electrical contacts are formed from a stainless steel foil that isetched to define filaments. The contacts are separated by a gap exceptwhen joined by the filaments. The stainless steel foil is provided on apolyimide substrate 34. Again the filaments provide the vast majority ofthis resistance, so that the majority of the heat is produced by thefilaments. In this example the filaments have an electrical resistancemore than 100 times higher than the electrical contacts.

In the cartridge shown in FIG. 3 , the contacts 32 and filaments 36, 38are located between the substrate layer 34 and the housing 24. However,it is possible to mount the heater assembly to the cartridge housing theother way up, so that the polyimide substrate is directly adjacent tothe housing 24.

Although the embodiments described have cartridges with housings havinga substantially circular cross section, it is of course possible to formcartridge housings with other shapes, such as rectangular cross sectionor triangular cross section. These housing shapes would ensure a desiredorientation within the corresponding shaped cavity, to ensure theelectrical connection between the device and the cartridge.

The capillary material 22 is advantageously oriented in the housing 24to convey liquid to the heater assembly 30. When the cartridge isassembled, the heater filaments 36 may be in contact with the capillarymaterial 22 and so aerosol-forming substrate can be conveyed directly tothe heater. In examples of the invention, aerosol-forming substratecontacts most of the surface of each filament so that most of the heatgenerated by the heater assembly passes directly into theaerosol-forming substrate. In contrast, in conventional wick and coilheater assemblies only a small fraction of the heater wire is in contactwith the aerosol-forming substrate. The capillary material 27 may extendinto the interstices between the filaments 36.

In use the heater assembly operates by resistive heating. Current ispassed through the filaments 36 under the control of control electronics16, to heat the filaments to within a desired temperature range. Themesh or array of filaments has a significantly higher electricalresistance than the electrical contacts 32 and electrical connectors 19so that the high temperatures are localised to the filaments. The systemmay be configured to generate heat by providing electrical current tothe heater assembly in response to a user puff or may be configured togenerate heat continuously while the device is in an “on” state.Different materials for the filaments may be suitable for differentsystems. For example, in a continuously heated system, graphitefilaments are suitable as they have a relatively low specific heatcapacity and are compatible with low current heating. In a puff actuatedsystem, in which heat is generated in short bursts using high currentpulses, stainless steel filaments, having a high specific heat capacitymay be more suitable.

In a puff actuated system, the device may include a puff sensorconfigured to detect when a user is drawing air through the mouthpieceportion. The puff sensor (not illustrated) is connected to the controlelectronics 16 and the control electronics 16 are configured to supplycurrent to the heater assembly 30 only when it is determined that theuser is puffing on the device. Any suitable air flow sensor may be usedas a puff sensor, such as a microphone.

In a possible embodiment, changes in the resistivity of one or more ofthe filaments 36 or of the heater element as a whole may be used todetect a change in the temperature of the heater element. This can beused to regulate the power supplied to the heater element to ensure thatit remains within a desired temperature range. Sudden changes intemperature may also be used as a means to detect changes in air flowpast the heater element resulting from a user puffing on the system. Oneor more of the filaments may be dedicated temperature sensors and may beformed from a material having a suitable temperature coefficient ofresistance for that purpose, such as an iron aluminium alloy, Ni—Cr,platinum, tungsten or alloy wire.

The air flow through the mouthpiece portion when the system is used isillustrated in FIG. 1D. The mouthpiece portion includes internal baffles17, which are integrally moulded with the external walls of themouthpiece portion and ensure that, as air is drawn from the inlets 13to the outlet 15, it flows over the heater assembly 30 on the cartridgewhere aerosol-forming substrate is being vapourised. As the air passesthe heater assembly, vapourised substrate is entrained in the airflowand cools to form an aerosol before exiting the outlet 15. Accordingly,in use, the aerosol-forming substrate passes through the heater assemblyby passing through the interstices between the filaments 36, 37, 38 asit is vapourised.

Other cartridge designs incorporating a heater assembly in accordancewith this disclosure can now be conceived by one of ordinary skill inthe art. For example, the cartridge may include a mouthpiece portion,may include more than one heater assembly and may have any desiredshape. Furthermore, a heater assembly in accordance with the disclosuremay be used in systems of other types to those already described, suchas humidifiers, air fresheners, and other aerosol-generating systems.

FIG. 5 shows a diagram indicating the performance of three differentconfigurations of heater elements in a test to measure the totalparticulate matter (TPM) deliveries provided by the example heatingelements.

The heating elements tested were as follows:

Heater A—Aperture 5 mm×5 mm. Three heater elements arranged as for FIG.3 —each having a width of 1 mm. Approximate heater area 15 mm².Resistance approximately 1.2 Ohms. Power consumption 6 W.

Heater B—Aperture approximately 3 mm×3 mm. One heater element coveringwhole aperture. Approximate heater area 10 mm². Resistance approximately0.5 Ohms. Power consumption 6 W.

Heater C—Aperture 5 mm×5 mm. One heater element arranged as for FIG. 2A,having a width of 2 mm. Approximate heater area 10 mm². Resistanceapproximately 0.8 Ohms. Power consumption 4W.

A liquid-containing capillary material was mounted adjacent the heater.The liquid comprised by weight, 39% propylene glycol, 39% glycerine, 20%water, 2% nicotine.

A puff comprising an air flow of 55 ml per 3 seconds was passed over theheater during heating and the resulting aerosol entrained in the airflowis trapped on a fiberglass filter disc (Cambridge Pad). After the testrun of 45 puffs, the aerosol components are extracted from thefiberglass filter disc using an alcohol solution in a known way todetermine the total particulate matter (TPM) for that test run. The TPMper puff was calculated and is shown in FIG. 5 .

Heater B including the heater element covering the whole aperture provedto have the lowest TPM yield (Total Particulate Matter) of only 1.1milligramm per puff. The heater assembly had a power consumption of 6Watts.

A higher TPM was observed with the heater C including only one 10 mm²heater element. With this heater assembly a TPM yield of about 2.2milligramm per puff was achieved, while at the same time the powerconsumption only amounted to 4 Watts. Thus, a higher TPM was seen for aheater element of similar size to that of Heater B, even at lower power.

Without wishing to be bound by any particular theory, it is thought thatfor Heater C, where the edges of the heater are spaced from the apertureedge, there is less heat transfer to the substrate element. Also, it isthought that for heater B, some of the heat heats liquid underneath thesubstrate element and that that liquid is unable to be released throughthe aperture, thus leading to less efficient use of heat from the heaterelements.

For Heater A including three heater strips, the TPM is also greater thanfor Heater B. Without wishing to be bound by any particular theory, TPMfor Heater A may be lower than that for Heater C because the three 1 mmstrips have a greater contact length with the edge of the aperturecompared with the single 2 mm strip of Heater C which may lead to moreheat transfer to the substrate or more ineffective heating of liquidunderneath the substrate.

The exemplary embodiments described above illustrate but are notlimiting. In view of the above discussed exemplary embodiments, otherembodiments consistent with the above exemplary embodiments will now beapparent to one of ordinary skill in the art.

We claim:
 1. An aerosol-generating system, comprising: anaerosol-generating device comprising a power source; and a cartridgeremovably coupled to the aerosol-generating device, the cartridgecomprising: a liquid storage portion comprising a housing having an openend and containing a liquid aerosol-forming substrate, a substantiallyflat heater assembly fixed to disposed at the open end of the housingand comprising an electrical heating element configured to heat theliquid aerosol-forming substrate to form an aerosol, the electricalheating element being both substantially flat and arranged in a curvedmanner, a capillary material disposed in contact with the electricalheating element and comprising a ceramic or a ceramic-based material,the capillary material being configured to convey the liquidaerosol-forming substrate to the electrical heating element, and aplurality of air inlets and an air outlet, wherein the liquid storageportion is disposed at a first side of the heater assembly and anairflow channel is disposed at a second side of the heater assembly, theairflow channel defining an airflow path over the heater assembly andconfigured to convey the aerosol, and wherein the power source of theaerosol-generating device is configured to supply power to thesubstantially flat heater assembly.